1. Technical Field
The present invention generally relates to grinder pumps. More particularly, the present invention relates to stations used to house grinder pumps.
2. Background Information
Today, low pressure sewer systems, powered by grinder pumps, are a desired alternative to conventional gravity sewer systems and septic tank use. Sewage grinder pump systems are now a widely accepted and popular means for handling residential waste, where conventional gravity sewer systems may not be practicable, or are expensive, requiring high priced materials and significant labor. Environmental concerns have also forced many communities to seek alternatives to both conventional gravity sewer systems and septic tank use. By keeping costs at a minimum and providing effective wastewater storage, conditioning, and transport, grinder pump systems provide a rational and cost effective alternative to conventional wastewater management systems.
While the costs associated with the installation, operation, and maintenance of grinder pump systems are significantly less than that of conventional gravity sewer systems, grinder pump installation remains a significant component of the overall cost of a sewage grinder pump system. Prior to installation of a grinder pump, an engineer or surveyor will typically determine the height of a housing for the grinder pump, also called a grinder pump station, needed for a particular site. Notwithstanding this pre-installation height determination, it is common to encounter obstructions in the field, e.g., a bed of rocks, etc., requiring at times a more expensive excavation and installation effort. An alternative to additional excavation is modification of the height of the grinder pump station in the field.
In the past, fiberglass has been the preferred material for grinder pump stations. While non-corrosive fiberglass has performed its function satisfactorily, several disadvantages are now apparent. First and foremost, fiberglass is a relatively expensive material. Height modification in the field is also difficult with fiberglass stations. Typically, height adjustment is limited to large increments, such as, eighteen inches. Large incremental modifications, however, do not provide adequate flexibility in adjusting height of grinder pump stations in the field.
Another disadvantage associated with fiberglass grinder pump stations is that after installation, the smooth walled fiberglass may be pushed or driven by buoyant groundwater forces, causing the stations to "float" from their installed location. In order to prevent such movement, concrete ballasting of the stations is often necessary. Concrete ballasting, however, requires a greater excavation and installation effort, ultimately adding additional expense. Another problem encountered with fiberglass grinder pump stations is groundwater leak paths which may emerge through the walls of the stations. These leak paths tend to occur where inlet, outlet, and interface openings are prepared in the field during installation.
Fiberglass grinder pump stations also have a limited tolerance to mishandling, which commonly occurs during shipment and installation. Transport and installation is often rough, and as a result, fiberglass stations may suffer structural damage during handling. Unfortunately, however, station damage may not be ascertainable until after installation is complete and leaking begins. Fiberglass also has a limited ability to withstand the abrasive effects associated with sewage slurry.
In order to compensate for the various drawbacks associated with fiberglass stations, it is believed that stations made of other materials are now available. One known non-fiberglass grinder pump station includes a rotationally molded station formed from polypropylene. While this known station avoids the usage of fiberglass, it retains many of the drawbacks associated with fiberglass stations, including difficult field height adjustment and limited structural integrity. In addition, this rotationally molded polypropylene station is not available with the grinder pump installed therein, and therefore, installation in the field remains laborious. Installation of the grinder pump in the field also aggravates the emergence of ground water leak paths through the various inlet and outlet openings of the station created during installation.
Thus, a need exists for a grinder pump station which possesses improved structural integrity, enjoys simple installation, allows field height modification in small increments without interfering with electrical and ventilation interfaces, and is highly resistant to corrosion, all at a reasonable cost.